Western Digital releases 1TB laptop hard drive | Crave - CNET
Be careful, the new WD's *might* not fit in a 2.5" slot.
Whatever you buy, buy an external drive as large as you can afford, back up your primary data at least once a week if not daily, it's as simple as a scheduled copy from the internal to the external.
I've had very good experience with WD HDD's, there was a period where they had a reliability issue, but that was a long time ago. You can buy WD's, they're fine. Every HDD manufacturer has had an rep issue along the way.
As always, get teh fastest RPM drive you can, don't worry about how many platters there are, I can't imagine you having an application that will be significantly affected or take advantage of a laptop hard drive read/seek/write times based on # of platters. RPM and cache are the 2 biggest features you should be concerned about.